At the Tulsa gun show last month there was a new vendor of a 45 upper that fits a receiver of the AR15/M16 platform, I bought 5 kits. Two of them needed modified with the bolt carrier cut for Sear trip and upper receiver cut for sear clearance. This is the one I did for my gun.

It takes std. grease gun mags in the side and ejects out the std. .223 magazine well.